Chemical shippers are urging federal regulators to deny a request by Union Pacific Railroad (UP) for permission to refrain from transporting chlorine over long distances because of safety concerns (C&EN, March 23, page 29). If the request is granted, "the entire common carrier obligation to transport toxic inhalation hazards will be threatened," the National Association of Chemical Distributors (NACD) says in comments filed with the Surface Transportation Board, a federal regulatory agency. Under federal law, rail carriers are required to quote rates and provide service for all legitimate shippers. But UP is questioning whether it should be forced to haul chlorine from a producer in Utah to customers in Texas and Louisiana, saying the transfer would pose "remote, but deadly, risks" as the shipments pass through densely populated urban areas. Railroads have expressed concern about their liability in the event of an accident in a major city. But NACD says the common carrier obligation "exists for the specific purpose of requiring the railroads to provide service to shippers when they would otherwise choose not to do so because it would be unprofitable or inconvenient." The obligation is the "only recourse that shippers have to ensure they are able to receive the rail service they need to safely and efficiently transport their products, particularly hazardous materials."